Pick-resistant lock

ABSTRACT

A cylinder lock having a plurality of pin assemblies selectively configured to engage a shoulder within the cylinder bore in the event that an attempt is made to pick the lock. In general, each pin assembly comprises a driver portion, a center portion, and a lower portion. The center and driver portions each contain unique transverse grooving which cooperates with the aforementioned shoulder to prevent pin movement if rotational pressure is applied to the plug without first inserting the proper key.

United States Patent [1 1 Hucknall PICK-RESISTANT LOCK [76] Inventor: Richard Hucknall, 3 Fairview Ave., Great Neck, NY.

22 Filed: Nov. 9, 1971 21 Appl.No.: 196,966

[52] US. Cl. 70/419, 70/378 [51] Int. Cl E05b 15/14 [58] Field of Search 70/364 A, 378, 376, 70/419, 421

[56] References Cited UNITED STATES PATENTS 2,629,249 2/1953 Mendelsohn 70/378 X 3,656,328 4/1972 Hughes 70/276 1,593,513 7/1926 Stone 70/378 X 2,059,129 10/1936 Maxwell... 70/364 A 2,283,489 5/1942 Crousore 70/378 X 3,681,955 8/1972 Sturgeon 70/363 1 Oct. 2, 1973 FOREIGN PATENTS OR APPLICATIONS 653,216 2/1963 Italy 70/378 Primary ExaminerRobert L. Wolfe Attorney-Robert R. Strack et al.

[57] ABSTRACT A cylinder lock having a plurality of pin assemblies selectively configured to engage a shoulder within the cylinder bore in the event that an attempt is made to pick the lock. In general, each pin assembly comprises a driver portion, a center portion, and a lower portion. The center and driver portions each contain unique transverse grooving which cooperates with the aforementioned shoulder to prevent pin movement if rotational pressure is applied to the plug without first inserting the proper key.

13 Claims, 8 Drawing Figures PATENIEUUBT 21915 I 11762193 SHEET 1 0F 2 FIG. 2 F I63 INVENTOR RICHARD HUCKNALL BY m 7 m ATTORNEYS Pmmmw'z 3.762.193 SHEET 2 0F 2 FIG.4E

FIG. 4 D

FIG. 4A

INVENTOR RICHARD HUCKNAL L g -BY amm 7 and ATTORNEYS PICK-RESISTANT LOCK BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to cylinder locks and more particularly to improved cylinder locks which are exceptionally resistant to existing lock picking techniques.

2. Description of the Prior Art In the general type of lock contemplated by this invention, there is a plurality of tumblers in the form of cylindrical pins which are mounted in radial holes in a cylindrical barrel or key plug. The lower end of these tumblers project into a slot provided for a key. The barrel or key plug is surrounded by a cylinder which has a number of radial holes corresponding to those in the plug. This cylinder houses a further set of cylindrical pins which may be pressed towards the center of helical springs. The pins in the outer cylinder are termed the drivers.

When there is no key in the plug, the tumbler and project into the tumbler bores in the plug, preventing it from being turned. In order to open the lock, a key is inserted which has its various indentations defining selective recesses and projections which cause each of the tumblers to be held to a definite lifted position such that the dividing line between the drivers and tumblers in each bore coincides with the shear line between the outer cylinder and plug. When all pins are appropriately positioned, the plug is free to rotate.

There are two well recognized techniques for picking the conventional lock described. In accordance with a first technique, the plug is turned relative to the cylinder, to the maximum extent allowed by the clearance between the pins and their respective bores. While maintaining torque upon the plug, each tumbler is pushed upward in turn, so that the driver associated with it is pushed up into its bore in the cylinder until it comes to rest at the shear line due to the ledge created by the slightly rotated position of the plug. When all drivers have been pushed back up into the cylinder bore in this manner, the plug can be turned free.

In the second well recognized technique, the tumblers and associated drivers are all initially pushed upward so that the tumblers enter the driver bores. The plug is then rotated as far as it will go and the tumblers are allowed to drop to their normal positions clear of the driver bores under the action of the driver springs. This can be accomplished because at the beginning of their downward movement, the tumblers are already partly within the plug. On the other hand, the drivers are not capable of following theirtumblers because they will be stopped by the aforementioned ledges that are formed by the lack of registration between the plug and cylinder bores.

Quite a number of lock structures have been developed in an attempt to defeat the picking of locks by each of the above-described methods. The resulting structures, have included in various combinations the serration of grooving of the cylinder bores, the plug bores, the driver pins, and the tumbler pins. When transverse grooves are provided in the pins and bores, it will be understood that the pins cannot move freely except under prescribed conditions such as when their dividing line is coincident to the shear line between the cylinder and plug. This prevents a lock picker from the simple application of the afore-described techniques.

20. driver holes or bores are in alignment, and the drivers Itis another object of the invention to provide an im- On the other hand, with a knowledge of the structure of such locks a skilled lock picker may still sense the relative positions of the driver and tumbler pins and given sufficient time, open these locks.

SUMMARY OF THE INVENTION The lock of the present invention is an improved form of cylinder lock wherein the cylinder bore, plug bore, and pin structure are designed cooperatively in order to prevent their being forced up or permitted to drop down while torque is applied to the key plug.

It is an object of the present invention to provide an improved pick-resistant cylinder lock.

It is another object of the present invention to provide an improved cylinder lock utilizing pins having selectively disposed and uniquely designed transverse indentations along their surface.

It is another object of the invention to provide an improved pick-resistant cylinder lock which can be easily manufactured.

proved cylinder lock which can be manufactured by modification of existing locks, if desired.

In accordance with an illustrative embodiment of the invention, there is provided a cylinder lock having cylinder and plug portions, each being radially bored to receive a plurality of pins of specific design, the diameter of the cylinder bores being greater than that of the plug bores. At the base of each cylinder bore, in close proximity to the shear line between plug and cylinder, a shoulder is provided which projects into the cylinder bore by an amount to provide an internal diameter substantially equivalent to that of the plug bore. This shoulder is configured to compliment indentations appearing on the surface of the driver and center pin, which comprise part of the pin assembly in each bore.

The objectives already mentioned, as well as further objects and the numerous unique features of the invention, will be fully understood and appreciated from the following detailed description of the invention, which is made in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view,.partially in crosssection, of a cylinder lock embodying the features of this invention;

FIG. 2 is an enlarged cross-sectional view taken along the lines 22 in FIG. 1, illustrating the position of a typical pin when the plug is not under rotational pressure;

FIG. 3 is an enlarged cross-sectional view taken along the lines 22 in FIG. 1, illustratingthe position of a typical pin arrangement when the plug is subjected to rotational pressure; and

FIG. 4A through 4E illustrate various pin assemblies that may be employed in a typical five pin cylinder lock.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The cylinder lock 10, shown in FIG. 1, cooperates with a typical key 11, having a shank 12 adapted for positioning within a key slot 13. The configuration of the key conforms to axially aligned projections in the key slot, such as 14, and includes projections of selected height for correct radial positioning of the various pin assemblies. The cylinder lock includes a cylinder portion 20 and a plug portion 21 adapted for rotation therein. The cylinder portion contains a plurality of axially displaced radially disposed bores 31, 32, 33, 34, and 35. The plug portion includes a similar plurality of bores which are aligned with the cylinder bores .when the lock is in its closed or rest position. These plug bores are illustrated as 41, 42, 43, 44, and 45 respectively. Each pair of associated bores in the cylinder and plug establish the radial chamber within which the pin assemblies operate. As described more fully hereinafter, and as illustrated in the following drawings, each pin assembly of the present invention may be made up of two or more components comprising a driver pin, a center pin, and a lowe pin. The center and lower pins within bore 45 are illustrated in FIG. 1 by elements 16 and 17, respectively.

FIGS. 2 and 3 illustrate the main components of a cylinder lock made in accordance with the principles of this invention. FIG. 2 is a transverse vertical section showing the plug bore aligned with the cylinder bore, when a key. is initially inserted. In contrast, FIG. 3 shows a similar transverse vertical section through the same bores when a key is not inserted; but with the plug subjected to torque, as when picking is attempted.

ltwill be noticed that the pin assembly in the illustrative embodiment is made up of a driver portion 69, a center pin 49 and a lower pin 50. The center and lower pins make up the tumblers. Lower pin 50 is substantially conventional in form and function. It may be provided at its lower edge with a crowned end, which rides up and over the ridges and valleys on a key. On its upper end, it is provided with a substantially flat surface which meets along a line 58 with lower complementary surface of the center pin 49,

Center pin 49 is cylindrical and has a lower portion 57 with a diameter substantially the same as the diameter of plug bore 41, but sufficiently smaller to permit it to move therein without binding. The upper end of center pin 49 has a number of axially displaced transverse notches 52, 53, alternating with a plurality of lands 54,

55, and 56. The topof the pin terminates in a surface 59 that is slightly crowned to correspond with the general radius of the plug. As seen in FIG. 2, when a key 12 of proper configuration is inserted in the lock, the top of center pin 49 falls along the shear line 22 between cylinder and plug 21.

Driver pin 60 includes an upper shank portion 66 that fits within a compressed coil spring 67 which exerts a downward bias thereon. The coil spring is anchored at its upper end by a suitable upper plug 68 and generally acts upon shoulder 65 of the driver in a conventional fashion. The central portion of driver 60 is of a constant diameter which substantially corresponds to the diameter of the plug bore, and the bottom portion includes transverse notch 61 and adjacent land 62. This bottom portion terminates in an end face 63 that preferably is crowned and which lies along the shear line 22 when the pin assembly is properly positioned to open the lock. As explained and illustrated hereinafter, the various notches and lands may appear in either the drive pin or center pin, depending upon the particular permutation and combination of pin assembly positions, selected for individual locks.

Consideration of FIG. 3, will assist in appreciating why the lock of this invention is substantially pickproof, even though its structure is known to the picker. For simplicity of explanation, assume that the lock has only one pin assembly.

If picking is attempted using the first technique mentioned above, clockwise torque is applied to the plug and the pin assembly is pushed slowly'upward. As soon as the first notch 61 reaches shoulder 37 there will be a noticeable freedom permitting further rotation of plug 21. If the picker releases the tumblers, lower pin 50 and center pin 49 will drop; however since the bottom of the driver is below the shear line between cylinder 20 and plug 21, the lock will not open. Furthermore, the picker cannot tell if both the center and lower pin dropped, or if only the lower pin dropped. Thus, the picker cannot know whether the driver or center pin is preventing rotation and accordingly does not know which direction to move the pin assembly in. Of course, with only one pin assembly, trial and error will quickly resolve any lack of knowledge, but when pluralities of bores and pin assemblies are involved, trial and error will be of no avail.

If picking is attempted using the second technique mentioned above, the pin assembly would first be pushed up into the cylinder bore until travel stops and then torque is applied to the plug 21. At this time, lower pin 50 will drop, but center pin 49 will engage one of its notches with shoulder 37 in the cylinder bore. Once again, the lock will not open and the picker cannot tell if driver or center pin is preventing rotation. Heretoo, trial and error will permit one to discover the actual condition when only one pin assembly is involved, but once again it must be appreciated that in an actual case plura'lities of bores and pin assemblies will be used.

As explained hereinafter, the invention does not rely merely upon an increase in thenumber of pin assemblies to frustrate lock pickers. The various notches and lands are also specifically designed with respect to the bores and each other to further prevent picking.

The angle of each notch is the same and is complementary to the angle of shoulder 37 in the cylinder bore. This assures seating of the notches against the shoulder in the event picking is attempted. It also makes manufacture of the pins easier and more economical. I

The lands between each notch all taper inwardly toward the top of the pin, preferably with the same constant slope. Thus, if a picker pushes the pin assembly upward while applying torque to the plug he will not be able to detect when the appropriate point on a land is adjacent to shoulder 37 for opening the lock. In some instances, it may be desirable for the land to merge and become part of one side of the notch, such as illustrated by land 55 at notch 53.

The maximum diameter of each'land also varies, and in fact, larger and smaller diameter lands may advantageously be alternated along the axis of the pin assembly. This arrangement of lands makes it impossible for a picker to hold up the pin assembly on a smaller diameter by pressure on the plug as he manipulates other pin assemblies, because the other assemblies will inevitably force the plug back in order to get sufficient clearance for axial movement. When the plug is forced back, the pin assembly originally supported at the smaller land will drop free. 4

A further important feature of the pin assembly of this invention concerns its overall length and the individual lengths of the various portions vis a vis otherv components of the cylinder lock. The relative lengths of the center pin 49 and lower pin50 are selected so that when the lock is in its rest position with the tumblers on key slot projection 24, the separating line 58 between lower pin 50 and center pin 49 is above the top 23 of key slot 13. In addition, the combined total length of the driver 60, center pin 49 and lower pin 50 is the same for every pin assembly; on the other hand, the driver 60 must be of such length relative to the cylinder lock, that when the assembly is together and the shank of 66 engages plug 68, the bottom of the center pin 49 is below the shear line.

Another aspect of the invention concerns the relative dimensions of the cylinder bore 31 and plug bore 41.

As previously noted, plug bore 41 has slightly greater diameter than the general diameter of pins 49, 50 and 60. Cylinder bore 31 is considerably larger than this, being necked down only at shoulder 37. The internal diameter at shoulder 37 corresponds to the plug bore diameter and this fact keeps the pins aligned when the driver 60 descends in the plug bore 41. It will be seen that, at rest, center section 64 of the driver will bear against the inner tip of shoulder 37, which provides the least possible clearance for initial twisting of the plug. With respect to manufacture, the bores in both the cylinder and plug can quite easily be made without need for special tooling and multiple operations.

FIGS. 4A through 4E illustrate five possible pin assemblies embodying the invention which can be employed in cylinder locks of conventional dimensions. The position of each assembly relative to these pin assemblies differ with respect to whether the grooving arrangement appears on the upper portion of the center pin 49 or the lower portion of the driver 60. It will be understood that various permutations and combinations of arrangements are permitted. Each pin assembly is characterized by the features discussed hereinabove. Thus, it will be seen that each of the notches exhibit the same angle, each of the lands exhibit the same inward tapering slope; and the wider and narrower land portions alternate. These figures, illustrate five distinct transverse notch arrangements, but of course, the number of grooves utilized will depend upon the size of the cylinder and plug assembly.

It will be seen that FIGS. 4A and 48 suggest the possibility that in certain acceptable pin assembly configuration, the center pin 49 and lower pin 50 may be merged into a single integral element. This occurs when substantially all of the notches are on the driver 60.

A final point of interest that can be derived from FIGS. 4A through 4E, concerns the location of the driver 60 when the various pin assemblies are correctly positioned for opening. In each case, it should be noted that the approximate center of the lowermost land on the driver, is opposite the tip of cylinder bore shoulder 37.

A rather specific embodiment of the invention has been shown and described. It is appreciated that those skilled in the art may make modifications in the various elements of the illustrated embodiment. All such modifications as come within the spirit and teachings of this disclosure, are intended to be covered by the appended claims.

What is claimed is:

1. A cylinder lock comprising a cylinder and a key plug positioned for rotation therein, a key slot in said plug and a radial plug bore extending from said key slot to the periphery of said plug, a radial cylinder bore extending through said cylinder and in axial registration with said plug bore, said cylinder bore being of a constant diameter that is larger than that of said plug bore and having a single internal projection at the end thereof adjacent to said plug, said internal projection leaving an opening substantially equal to the diameter of said plug bore; and a pin assembly within said bores having at least two axially displaced elements, each element having a diameter to provide a sliding fit within said plug bore, and at least one of said elements having a plurality of transverse notches complementing said projection.

' 2. A cylinder lock as defined in claim 1, wherein the combined axial length of said pin assembly is greater than the length of said cylinder bore and the parting line between said elements falls along the shear line between said cylinder and plug when the lowermost element projects a predetermined distance into said key slot.

3. A cylinder lock as defined in claim 2, wherein said transverse notches are present in each of said elements in proximity to said parting line.

4. A cylinder lock as defined in claim 2, including a third element in said pin assembly positioned within said plug bore and adjacent to said key slot.

5. A cylinder lock as defined in claim 4, wherein the combined axial length of said first two elements exceeds the length of said cylinder bore.

6. A cylinder lock as defined in claim I, wherein all of said transverse notches have at least one wall forming a predetermined angle relative to the axis of said elements.

7. A cylinder look as defined in claim 1, wherein said notches are axially spaced along said pin assembly and are separated by lands.

8 A cylinder lock as defined in claim 7, wherein said lands taper inward toward the end of said assembly remote from said plug and the slope of said lands is constant.

9. A cylinder lock as defined in claim 8, wherein the maximum diameter of each of said lands differs.

10. A cylinder lock as defined in claim 9, wherein adjacent lands alternately exhibit greater and lesser maximum diameters.

11. A cylinder lock as defined in claim 1, wherein said projection in the cylinder bore is in the form of a continuous internal shoulder located adjacent to the shear line between said cylinder and plug, said shoulder being formed of tapering converging surfaces terminating in a plane defining the smallest internal diameter within said cylinder bore.

12. A cylinder lock as defined in claim 1, wherein the element remote from said plug is biased in the direction of said plug.

13. A cylinder lock as defined in claim 1, comprising a plurality of cylinder bore, plug bore, and pin assembly combinations.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,762 ,193 Dated October 2, 1973 Inventors) Richard Hucknall It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 17 change "of" to --by-.

Column 1, line 61 change "of" first occurrence,

to -or-.

Column 3, line 13 change "lowe" to lower-- Column 5, line l3 afterT'has" insert -a---.

Signed and sealed this 5th day of March 19714..

(SEAL) Attest:

EDWARD M.FLETCHER, JR. c. MARSHALL DANN Atte sting Officer Commissioner of Patents F5. RM [Jo-150 (m'ss) USCOMM-DC 60376-P69- h U.S. GOVERNMENT PRINTING OFFICE: 1965 0-356-33 

1. A cylinder lock comprising a cylinder and a key plug positioned for rotation therein, a key slot in said plug and a radial plug bore extending from said key slot to the periphery of said plug, a radial cylinder bore extending through said cylinder and in axial registration with said plug bore, said cylinder bore being of a constant diameter that is larger than that of said plug bore and having a single internal projection at the end thereof adjacent to said plug, said internal projection leaving an opening substantially equal to the diameter of said plug bore; and a pin assembly within said bores having at least two axially displaced elements, each element having a diameter to provide a sliding fit within said plug bore, and at least one of said elements having a plurality of transverse notches complementing said projection.
 2. A cylinder lock as defined in claim 1, wherein the combined axial length of said pin assembly is greater than the length of said cylinder bore and the parting line between said elements falls along the shear line between said cylinder and plug when the lowermost element projects a predetermined distance into said key slot.
 3. A cylinder lock as defined in claim 2, wherein said transverse notches are present in each of said elements in proximity to said parting line.
 4. A cylinder lock as defined in claim 2, including a third element in said pin assembly positioned within said plug bore and adjacent to said key slot.
 5. A cylinder lock as defined in claim 4, wherein the combined axial length of said first two elements exceeds the length of said cylinder bore.
 6. A cylinder lock as defined in claim 1, wherein all of said transverse notches have at least one wall forming a predetermined angle relative to the axis of said elements.
 7. A cylinder lock as defined in claim 1, wherein said notches are axially spaced along said pin assembly and are separated by lands.
 8. A cylinder lock as defined in claim 7, wherein said lands taper inward toward the end of said assembly remote from said plug and the slope of said lands is constant.
 9. A cylinder lock as defined in claim 8, wherein the maximum diameter of each of said lands differs.
 10. A cylinder lock as defined in claim 9, wherein adjacent lands alternately exhibit greater and lesser maximum diameters.
 11. A cylinder lock as defined in claim 1, wherein said projection in the cylinder bore is in the form of a continuous internal shoulder located adjacent to the shear line between said cylinder and plug, said shoulder being formed of tapering converging surfaces terminating in a plane defining the smallest internal diameter within said cylinder bore.
 12. A cylinder lock as defined in claim 1, wherein the element remote from said plug is biased in the direction of said plug.
 13. A cylinder lock as defined in claim 1, comprising a plurality of cylinder bore, plug bore, and pin assembly combinations. 